1. FIELD OF THE INVENTION
The present invention relates, generally, to radiometers and, more particularly, to ultraviolet radiometers. Even more particularly, this invention relates to radiometers capable of measuring ultraviolet (UV) radiation in the UVA (320-400 nm), UVB (280-320 nm) and UVC (approximately 100-280 nm) ranges. Specifically, the present invention relates to an improved broadband ultraviolet radiometer exhibiting near flat spectral response over all (or selected portions) of the UVA, B and C.
2. DESCRIPTION OF THE PRIOR ART
There are many situations in which it is necessary or highly desirable to be able to measure the amount of a given wavelength light fraction (e.g., ultraviolet light) which is present in a light beam. For example, in research applications involving the use of electromagnetic optical radiation, the amount of ultraviolet radiation emitted by the source can be critical to the experiments being conducted. Also, in conducting photochemical reactions, the amount of ultraviolet radiation present normally must be known in order to properly quantify the reactions.
In certain medical applications where electromagnetic radiation is used it is also important to know the amount of ultraviolet radiation present. In various photovoltaic apparatus (e.g., solar cells) it is important to know the amount of ultraviolet radiation to which such apparatus is being exposed. Another common situation involves sun bathers and other persons who are outside during daylight hours and who are being exposed to harmful ultraviolet rays. Knowing the amount of ultraviolet radiation they are being exposed to would be very helpful so as to enable such persons to know the type and amount of sun screen lotion to apply to their exposed skin, for example.
The amount of solar ultraviolet radiation is a measure of the amount of ozone depletion in the earth's atmosphere. Such measurements at a number of global sites are urgently needed in order to assess the amount and global distribution of this depletion.
Various devices have been previously proposed for measuring ultraviolet radiation present in a light source. However, such devices have not been entirely accurate or satisfactory for all purposes.
U.S. Pat. No. 2,490,011 (Bird) describes an ultraviolet ray intensity meter which utilizes two vacuum photocells in a differential combination. The apparatus does not utilize an integrating sphere, nor does it address the requirement for a flat spectral response over the ultraviolet region being measured.
U.S. Pat. Nos. 3,609,364 (Paine); 3,825,760 (Fletcher); and 4,241,258 (Cholin) describe apparatus for detecting ultraviolet rays in the presence of broadband light, as in detecting flames in the presence of background light. The apparatus described in such patents is not an ultraviolet radiometer.
U.S. Pat. No. 3,896,313 (Berman) describes apparatus which is said to be able to detect the presence of ultraviolet light over a discrete wavelength band. Such apparatus does not provide the capability of accurately measuring the amount of ultraviolet radiation present in broadband radiation.
U.S. Pat. No. 3,562,795 (Frenk) describes apparatus for measuring the photometric intensity of one light beam against the photometric intensity of a reference beam. The apparatus does not measure the amount of ultraviolet energy in broadband radiation.
U.S. Pat. No. 4,915,500 (Selkowitz) describes a radiative flux mapping device. Such apparatus is not intended for measuring the amount of ultraviolet energy present in broadband radiation.
There has not heretofore been provided a broadband radiometer which exhibits essentially flat spectral response having the advantages and desirable combination of features which are exhibited by the apparatus and techniques of the present invention.